Scaffolding matrix with internal nanoparticles

ABSTRACT

A battery electrode composition is provided comprising composite particles, with each composite particle comprising active material and a scaffolding matrix. The active material is provided to store and release ions during battery operation. For certain active materials of interest, the storing and releasing of the ions causes a substantial change in volume of the active material. The scaffolding matrix is provided as a porous, electrically-conductive scaffolding matrix within which the active material is disposed. In this way, the scaffolding matrix structurally supports the active material, electrically interconnects the active material, and accommodates the changes in volume of the active material.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application for patent is a Continuation of U.S. patentapplication Ser. No. 17/353,364, entitled “Scaffolding Matrix withInternal Nanoparticles” filed on Jun. 21, 2021, which is a Continuationof U.S. patent application Ser. No. 16/419,806 entitled “ScaffoldingMatrix with Internal Nanoparticles” filed on May 22, 2019, which is aContinuation of U.S. patent application Ser. No. 13/973,943 entitled“Scaffolding Matrix with Internal Nanoparticles” filed on Aug. 22, 2013,which claims priority to Provisional Application No. 61/693,070 entitled“Scaffolding Matrix with Internal Nanoparticles” filed on Aug. 24, 2012,each of which is expressly incorporated by reference herein.

GOVERNMENT LICENSE RIGHTS

This invention was made with government support under Award IDDE-AR0000265 awarded by the Advanced Research Projects Agency-Energy(ARPA-E) within the United States Department of Energy (DOE). Thegovernment has certain rights in the invention.

BACKGROUND Field

The present disclosure relates generally to energy storage devices, andmore particularly to metal-ion battery technology and the like.

Background

Owing in part to their relatively high energy densities, light weight,and potential for long lifetimes, advanced metal-ion batteries such aslithium-ion (Li-ion) batteries are desirable for a wide range ofconsumer electronics. However, despite their increasing commercialprevalence, further development of these batteries is needed,particularly for potential applications in low- or zero-emissionhybrid-electrical or fully-electrical vehicles, consumer electronics,energy-efficient cargo ships and locomotives, aerospace applications,and power grids.

Materials that offer high capacity for such batteries includeconversion-type electrodes (e.g., metal fluorides, sulfides, oxides,nitrides, phosphides and hydrides and others for Li-ion batteries),alloying-type electrodes (e.g., silicon, germanium, tin, lead, antimony,magnesium and others for Li-ion batteries) and others. The majority ofsuch materials suffer from several limitations for various metal-ionbattery chemistries, including: (i) low electrical conductivity, whichlimits their utilization and both energy and power characteristics inbatteries; (ii) low ionic conductivity, which limits their utilizationand both energy and power characteristics in batteries; (iii) volumechanges during metal ion insertion/extraction, which may causemechanical and electrical degradation in the electrodes and(particularly in the case of anode materials) degradation in thesolid-electrolyte interphase (SEI) during battery operation; and (iv)changes in the chemistry of their surfaces, which may weaken thestrength of (or even break) the particle-binder interface, leading toelectrode and battery degradation.

Decreasing particle size decreases the ion diffusion distance, andoffers one approach to addressing the low ionic conductivity limitation.However, nanopowders suffer from high electrical resistance caused bythe multiple, highly resistive point contacts formed between theindividual particles. In addition, small particle size increases thespecific surface area available for undesirable electrochemical sidereactions. Furthermore, simply decreasing the particle size does notaddress and may in some cases exacerbate other limitations of suchmaterials, such as volume changes and changes in the external surfacearea of the particles, as well as weakening of the particle-binderinterfaces.

Certain high capacity materials, such as sulfur (S), additionally sufferfrom the dissolution of intermediate reaction products (e.g., metalpolysulfides) in the battery electrolyte, which further contributes totheir degradation. Although sulfur incorporation into porous carbons viamelt-infiltration has been shown to reduce dissolution and increaseelectrical conductivity of S-based cathodes, such techniques arenarrowly tailored to a limited set of materials with low melting pointslike sulfur (about 115° C.) and to a limited set of produciblestructures (e.g., conformal coatings).

Accordingly, there remains a need for improved batteries, components,and other related materials and manufacturing processes.

SUMMARY

Embodiments disclosed herein address the above stated needs by providingimproved battery components, improved batteries made therefrom, andmethods of making and using the same.

A battery electrode composition is provided comprising compositeparticles, with each composite particle comprising active material and ascaffolding matrix. The active material is provided to store and releaseions during battery operation. For certain active materials of interest,the storing and releasing of the ions causes a substantial change involume of the active material. The scaffolding matrix is provided as aporous, electrically-conductive scaffolding matrix within which theactive material is disposed. In this way, the scaffolding matrixstructurally supports the active material, electrically interconnectsthe active material, and accommodates the changes in volume of theactive material.

A method of fabricating a battery electrode composition comprisingcomposite particles is also provided. The method may comprise, forexample: providing an active material to store and release ions duringbattery operation, whereby the storing and releasing of the ions causesa substantial change in volume of the active material; and forming aporous, electrically-conductive scaffolding matrix within which theactive material is disposed, wherein the scaffolding matrix structurallysupports the active material, electrically interconnects the activematerial, and accommodates the changes in volume of the active material.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are presented to aid in the description ofembodiments of the invention and are provided solely for illustration ofthe embodiments and not limitation thereof.

FIG. 1 illustrates an example battery electrode composition according tocertain example embodiments.

FIG. 2 illustrates an example battery electrode composition designfurther incorporating a functional shell according to other exampleembodiments.

FIG. 3 illustrates another example battery electrode composition designincorporating a functional shell according to other example embodiments.

FIG. 4 illustrates another example battery electrode composition designincorporating a functional shell according to other example embodiments.

FIG. 5 illustrates another example battery electrode composition designincorporating a functional shell with a second active material accordingto other example embodiments.

FIG. 6 illustrates an example battery electrode composition designincorporating a multi-layered functional shell according to otherexample embodiments.

FIG. 7 illustrates another example battery electrode composition designincorporating a multi-layered functional shell according to otherexample embodiments.

FIG. 8 illustrates an alternative example battery electrode compositiondesign according to other example embodiments.

FIG. 9 illustrates an example battery electrode composition designincorporating an active material core and a functional shell accordingto other example embodiments.

FIG. 10 illustrates another example battery electrode composition designincorporating an active material core and a functional shell accordingto other example embodiments.

FIG. 11 illustrates an example battery electrode composition designincorporating external channel pores according to other exampleembodiments.

FIG. 12 illustrates an example battery electrode composition designincorporating external channel pores and a filler material according toother example embodiments.

FIG. 13 illustrates another example battery electrode composition designincorporating external channel pores and a filler material according toother example embodiments.

FIG. 14 illustrates another example battery electrode composition designincorporating external channel pores and a filler material according toother example embodiments.

FIG. 15 illustrates an example battery electrode composition designincorporating external channel pores and a functional shell according toother example embodiments.

FIG. 16 illustrates an example battery electrode composition designincorporating external channel pores, a filler material, and afunctional shell according to other example embodiments.

FIG. 17 is a flowchart illustrating an example method of fabricating abattery electrode composition according to various example embodiments.

FIG. 18 is a graphical flow diagram from a cross-sectional perspectivedepicting formation of an example composite particle of the typeillustrated in FIG. 1 or 3 according to certain example embodiments.

FIG. 19 is a graphical flow diagram from a cross-sectional perspectivedepicting formation of an example composite particle of the typeillustrated in FIG. 8 according to certain example embodiments.

FIG. 20 is a graphical flow diagram from a cross-sectional perspectivedepicting formation of an example composite particle of the typeillustrated in FIG. 4, 5, or 7 according to certain example embodiments.

FIG. 21 is a graphical flow diagram from a cross-sectional perspectivedepicting formation of an example composite particle of the typeillustrated in FIG. 5 or 7 according to certain example embodiments.

FIG. 22 is a graphical flow diagram from a cross-sectional perspectivedepicting formation of an example composite particle of the typeillustrated in FIG. 4 according to certain example embodiments.

FIG. 23 is a graphical flow diagram from a cross-sectional perspectivedepicting formation of an example composite particle of the typeillustrated in FIG. 4 or 6 according to certain example embodiments.

FIG. 24 shows SEM and TEM images of an example carbon scaffold particlefabricated with silicon nanoparticles deposited therein.

FIG. 25 illustrates an example battery (e.g., Li-ion) in which thecomponents, materials, methods, and other techniques described herein,or combinations thereof, may be applied according to variousembodiments.

DETAILED DESCRIPTION

Aspects of the present invention are disclosed in the followingdescription and related drawings directed to specific embodiments of theinvention. The term “embodiments of the invention” does not require thatall embodiments of the invention include the discussed feature,advantage, process, or mode of operation, and alternate embodiments maybe devised without departing from the scope of the invention.Additionally, well-known elements of the invention may not be describedin detail or may be omitted so as not to obscure other, more relevantdetails.

The present disclosure provides for advanced composite materials forbattery electrodes formed from a porous, electrically-conductive“scaffolding” matrix having active material(s) incorporated therein. Asdiscussed in more detail below, several advantages over conventionaldesigns are provided by incorporating active material into this type ofscaffolding matrix. For example, deposition of the active materialinside a scaffolding matrix (as opposed to surface deposition) helpsavoid the often undesirable agglomeration of individual active materialparticles.

Further, a portion of the scaffolding matrix can be left exposed and,therefore, used for the stable attachment of a (polymer) binder. A morestable particle-binder interface may lead to more stable performance ofthe electrode. The outer surface area of the scaffolding matrix can alsobe used for the deposition of an ionically conductive (and solventimpermeable) outer shell, thereby sealing the active material depositedinside the scaffolding matrix and avoiding the often undesirable contactof active material with solvent molecules of the electrolyte.

The scaffolding matrix may also be used to electrically connectindividual active (nano)particles, which is important for higherutilization of the active particles. Furthermore, the scaffolding matrixmay be capable of maintaining such electrical connectivity even in caseswhen active particles change dimensions during insertion and extractionof ions (during the battery operation, such as during charging anddischarging).

FIG. 1 illustrates an example battery electrode composition according tocertain example embodiments. Here, an individual composite particle 100is shown for illustration purposes. A battery electrode may be formedfrom a collection of such composite particles 100 (e.g., agglomeratedonto a current collector or the like) as appropriate for a givenapplication. The spherical shape is shown for illustration purposesonly, but may be beneficial for some applications.

The composite particle 100 includes an active material 102 and a porous,electrically-conductive scaffolding matrix 104. In this example, theactive material 102 is illustrated as a collection of individual active(nano)particles. In general, the characteristic dimensions of theindividual active particles (e.g., a diameter of individual activeparticles, in an idealized spherical case) may be in the range of about0.1% to about 50% of the characteristic dimensions of the compositeparticle 100. The active material 102 is provided to store and releaseions during battery operation.

As discussed above, for certain active materials of interest (e.g.,silicon), the storing and releasing of these ions (e.g., Li ions in aLi-ion battery) causes a substantial change in volume of the activematerial, which, in conventional designs, may lead to irreversiblemechanical damage, and ultimately a loss of contact between individualelectrode particles or between the electrode and underlying currentcollector. Moreover, it may lead to continuous growth of thesolid-electrolyte interphase (SEI) around such volume-changingparticles. The SEI growth, in turn, consumes ions and reduces cellcapacity.

The porous, electrically-conductive scaffolding matrix 104 is providedto address these issues by having the active material 102 disposedwithin its framework. In this way, the scaffolding matrix 104structurally supports the active material 102, electricallyinterconnects the active material 102, and accommodates the changes involume of the active material 102 discussed above. In general, thecomposite particles 100 may be able to accommodate changes in volume ofthe active material 102 during battery operation that exceed acorresponding change in volume of the scaffolding matrix 104 by morethan 100%.

More specifically, the use of a porous, electrically-conductivescaffolding matrix in this manner provides several advantages,including: (i) it electrically interconnects active particles; (ii) itprovides volume for particle expansion upon insertion of metal ions;(iii) it may provide paths for rapid access of ions into the surface ofthe particles; (iv) it provides a foundation for the deposition of anouter shell permeable to metal ions but not permeable to solventmolecules; (v) it provides sites for the stable attachment of a polymerbinder; and (vi) it supports facile routes for incorporation of theactive particles/materials via impregnation strategies.

Such advantages are provided for a wide range of high capacity anode andcathode materials, and particularly for high melting point materials(such as materials with a melting point greater than about 600° C.),although low melting point materials (such as Sn and In) may alsobenefit from various aspects of the disclosed techniques. In addition,advantages are particularly provided for high capacity anode and cathodematerials that exhibit significant volume changes (e.g., greater thanabout 10%) upon insertion and extraction of ions (e.g., metal ions). Foranodes that can be used in metal-ion (e.g. Li-ion) batteries, examplesinclude but are not limited to: heavily doped, doped and undoped Si, In,Sn, Sb, Ge, Mg, Pb, their alloys with other metals and semimetals, theirmixtures with other metals, metal oxides, metal fluorides, metaloxy-fluorides, metal nitrides, metal phosphides, metal sulfides andsemiconductor oxides. For cathodes that can be used in metal-ion (e.g.Li-ion) batteries, examples include but are not limited to: metalsulfides, metal fluorides, metal oxy-fluorides, and their mixtures, toname a few.

Even for high capacity (e.g., greater than about 250 mAh/g for Li-ionbattery cathodes and greater than about 400 mAh/g for Li-ion batteryanodes) electrode particles that do not experience dissolution duringbattery operation, stability as well as power characteristics may begreatly improved by the designs herein. This is particularly true foractive materials having low electrical conductivity (e.g., less thanabout 5 S/m) or active materials having a low diffusion coefficient forthe metal ions employed (e.g., less than about 10⁻¹¹ cm²/S).

It will be appreciated that various metal ions may be utilized inconjunction with the electrode material designs described herein.Examples include but are not limited to: Li⁺, Na⁺, Mg²⁺, Ca²⁺, and Al³⁺.The designs herein may be particularly attractive for metal ions with anion size larger than that of Li⁺ or an ion charge larger than +1. Thepresent invention is not limited to metal-ion batteries (and thus notlimited to metal ions), however, and can be used in other batterychemistries where active particles undergo significant volume changesduring their operation (e.g., reversible reduction-oxidation reactions),including, for example, aqueous electrolyte-containing batteries.

Returning to FIG. 1, it is noted that the desired pore size within thescaffolding matrix 104 may vary based on the desired application andcorresponding materials employed. In general, it may be advantageousthat the total volume of all the pores within the scaffolding matrix 104is made sufficient to provide space for the volume expansion of theactive material 102 during ion insertion. For active nanoparticles withcharacteristic dimensions typically on the order of about 3-100 nm,pores in the range of about 0.4 nm to about 50 nm have been found towork well. In some cases, the combination of micropores (e.g., less thanabout 2 nm) and mesopores (e.g., on the order of about 2-50 nm) withinthe scaffolding matrix 104 may be further beneficial, while in otherdesigns, it may be advantageous to simply employ mesopores. As anexample, a volume of mesopores within a porous (e.g., carbon) matrix inexcess of about 0.05 cc/g_((Carbon)) has been found to work well.

In some designs, it may be advantageous for high capacity activeparticles embedded into a scaffolding matrix to be formed in such a waythat a portion of the scaffolding matrix penetrates into the activeparticles (e.g., such that the particles are formed around one or morescaffold pore walls) or that the individual high capacity activeparticles connect several pore walls of the scaffolding matrix. Thishelps enhance the structural and electrical stability of the compositeduring battery operation and expansion/contraction of the activeparticles during insertion and extraction of ions.

One example of a scaffolding matrix material that may be employed invarious designs is a porous carbon material. However, various otherporous, electrically-conductive materials may also be employed. Forexample, conductive porous polymer scaffold particles may be usedinstead of porous carbon scaffold particles in other designs. Further,in some designs it may be advantageous to introduce additionalfunctional groups or other materials into the inner surface of thescaffolding matrix in order to encourage, for example, heterogeneousnucleation (or attachment) of nanoparticles of the active materialinside. Doping of either a porous carbon or a produced composite withelements (such as nitrogen) that enhance the composite electrical orionic conductivity may also be beneficial for using these composites inelectrodes of metal-ion batteries. For certain applications in Li-ionbatteries, it may also be advantageous to introduce Li into, forexample, a porous carbon-nanoparticle composite. Similarly, inapplications of the composite material in batteries based on othermetals, it may be advantageous to introduce the same metal as the ionsutilized into the scaffolding matrix.

Several example methods of fabrication for an active material infusedscaffolding matrix are described below. The fabrication techniques allowefficient and controlled incorporation of nanoparticles ofelectrochemically active battery materials with high melting points(e.g., greater than about 600° C.), for example, or with no meltingpoint (when the materials would simply decompose at high temperature),into a porous carbon matrix, by way of example.

In one example, active nanoparticles may be introduced into apre-fabricated porous carbon matrix/scaffold particles via chemicalvapor deposition (CVD). Porous carbon particles may be fabricated bychemical synthesis or precipitation driven fabrication or combination ofthe chemical and precipitation methods of polymeric precursor particles,their pyrolysis (thermal treatment) and activation (partial oxidation tointroduce or increase the volume of interconnected pores). Desired poresizes and their distribution may be achieved, for example, by acombination of porosity in the polymer precursor and a carbon activationprocess. Another way to produce porous carbon scaffolds includessynthesis of a large polymer monolith, its carbonization, and mechanicalgrinding of the carbon monolith into particles of the desired shape. Theactivation process may involve physical oxidation with oxygen-containinggases (such as CO₂, H₂O, air, O₂, etc.), chemical activation (e.g., withKOH) or a combination of these approaches. The activation may beperformed during or after the thermal treatment. In order to introduceboth micropores and mesopores (which may in some cases be beneficial, asdiscussed above), carbon activation may be performed at differenttemperatures (e.g., at about 800 and about 1000° C.) or using differentactivation agents (e.g., CO₂ and H₂O). In some cases, it may bebeneficial to introduce mesopores into the porous carbon by utilizing amixture of two polymers (or carbon yielding polymer mixture with organicliquid) within the polymeric precursor particles. In some cases, theorganic liquid can be a non-solvent for the polymer or the polymer canbe swollen in that liquid. The non-solvent/solvent nature of the liquidwill define the pore sizes and distribution of the pores. One of thepolymers can be either removed after synthesis of the polymericparticles by selective extraction or one of the polymers may inherentlyexhibit low thermal stability or very low carbon yield duringcarbonization or after activation, or both. In some cases, pores may beintroduced into the surface of dense carbon particles (such as syntheticor artificial graphite, mesocarbon microbeads, etc.). In one example,metal or other inorganic nanoparticles may be pre-deposited on thesurface of carbon to serve as catalysts for etching or oxidation ofpores within the carbon. In another example, extractable,non-carbonizing nanoparticles may be introduced into the polymerparticles subjected to carbonizations. In other examples, a carbonporous scaffold may be made by carbon deposition (CVD for example) on ahighly porous scaffold made from inorganic material. Silica aerogels areone example of such inorganic scaffolds for carbon deposition.

According to another example method, active particles may be introducedinto a pre-fabricated porous carbon matrix via vapor infiltration and/orcapillary condensation. This approach may be particularly attractive formaterials that have high vapor pressure (e.g., greater than about 0.1Pa) at moderately high temperatures (e.g., less than about 1000° C.).

According to another example method, active particles may be introducedby: (i) dissolving active particles or active particle precursors in asolvent; (ii) infiltration of the solution into the pores of apre-fabricated porous carbon matrix under normal pressure, at increasedpressure, or under vacuum; (iii) evaporation of the solvent; and (iv)(if needed) transformation of the precursor into the active particles.In some cases, some of the above steps may be repeated to increase thetotal amount of the introduced nanoparticles of active material into theporous carbon matrix.

According to another example method, active particles may be introducedby: (i) dissolving active particles or active particle precursors in asolvent; (ii) infiltration of the solution into the pores of apre-fabricated porous carbon matrix under normal pressure, at increasedpressure, or under vacuum; (iii) heterogeneous precipitation ofnanoparticles on the inner carbon surface from the solution by, forexample, adding a non-solvent, changing the ionic strength or the pH ofthe solution, or changing the temperature/pressure of the system; and(iv) (if needed) transformation of the precursor into the activeparticles. In some cases, some of the above steps may be repeated orcombined to increase the total amount of the introduced nanoparticles ofactive material into the porous carbon matrix.

According to another example method, active particles are introduced byinfiltration of nanoparticles of active materials into the pores ofpre-formed porous carbon using a suspension infiltration method undernormal pressure or at increased pressures or under vacuum.

According to another example method: (i) active nanoparticles may firstbe adsorbed onto the surface of the nanoparticles of a polymericprecursor for carbon formation (e.g., by introduction of the oppositecharge on the surface of the active nanoparticles and the surface of thepolymer precursor nanoparticles); (ii) thermal treatment that inducescarbonization of the polymer precursor and the formation of thenanocomposite comprising active nanoparticles, carbon, and nanopores;and (iii) optional activation to increase the volume of pores. Inanother example, after the nanoparticle deposition, the compositepolymer particles may be covered with another carbon-forming ornon-carbon forming polymer layer by the electrostatic adsorption of apolymer having opposite surface charge than that of the particles.

According to another example method: (i) active nanoparticles andpolymer precursor nanoparticles may be coagulated heterogeneously from asolution/suspension to form larger composite-precursor particles; (ii)thermal annealing (carbonization) to form the nanocomposite withnanoparticles uniformly distributed within carbon and pores; and (iii)optional activation to increase the volume of pores.

According to another example method, the following may be performed: (i)active nanoparticles may first be dispersed in a monomer or polymersolution; (ii) the produced suspension may be emulsified (e.g., inwater) to produce spherical nanoparticle-polymer colloids in water;(iii) the monomer in the colloids may be polymerized (or solvent may beextracted from a polymer solution) to produce the spherical compositeparticles composed of active nanoparticles and a polymer; (iv) uponwater evaporation the composite particles may be carbonized; and (v) theproduced carbon-active nanoparticle composite may (optionally) beactivated to increase the volume of pores. In another example,polymerization may be conducted in a non-aqueous solvent for a monomer,which is a non-solvent for the polymer being synthesized. During thepolymerization, the polymer particles may be formed by a precipitationmechanism. In the course of the precipitation, polymerization of theactive nanoparticles becomes captured inside the polymer particles. Uponparticle separation, the composite particles may be carbonized.

According to another example method, the following may be performed: (i)water with active particle precursors may be emulsified in a monomersolution; (ii) the produced mixture may be emulsified in water again toproduce colloids of the monomer solution (inside of which there arecolloids of active particle precursor); (iii) the monomer may bepolymerized producing near-spherical polymer particles containing thedistribution of precursors of active particles; (iv) the producedemulsion may be dried, calcinated/carbonized to produce porous carbonparticles with incorporated nanoparticles of active material; and (v)the produced carbon-active nanoparticle composite may (optionally) beactivated to increase the volume of pores. An analogous approach can berealized in a non-aqueous medium as mentioned above.

According to another example method, the following may be performed: (i)an active particle precursor may be dissolved in an organic solventalong with a suitable carbon forming polymer; (ii) the homogeneoussolution may be mixed with an excess of a non-solvent for the particleprecursor and the polymer, and composite particles may be formed byprecipitation; (iii) the produced particles may be dried,calcinated/carbonized to produce porous carbon particles withincorporated nanoparticles of active material. In another example, theprecipitation may be conducted via changing ionic strength or pH of thesolution, or changing temperature/pressure of the system.

In some designs as provided for herein, electrode stability may befurther enhanced by a “shell” coating, such as an additional ion (e.g.,a metal ion in case of a metal-ion battery, such as a Li ion in case ofa Li-ion battery) permeable but electrolyte solvent impermeable, thinlayer coating (e.g., on the order of about 1-50 nm).

FIG. 2 illustrates an example battery electrode composition designfurther incorporating a functional shell according to other exampleembodiments. As shown, the composite particle 200 of FIG. 2 includes theactive material 102 and the porous, electrically-conductive scaffoldingmatrix 104 within which the active material 102 is disposed, as in thedesign of FIG. 1, and further includes a shell 208 at least partiallyencasing the active material 102 and the scaffolding matrix 104. Ingeneral, the shell 208 is made substantially permeable to the ionsstored and released by the active material 102, but may otherwiseprovide different functionality as desired for different applications.

In the particular example illustrated in FIG. 2, the shell 208 isspecifically, or otherwise includes, a protective layer formed from amaterial that is substantially impermeable to electrolyte solventmolecules. In the case of a low-voltage anode used in metal-ionbatteries, such as an anode with a reduction-oxidation reactionoccurring below about 1 V vs. Li/Li+ in a Li-ion battery, the protectivelayer of the shell 208 also provides a more stable outer surface for theSEI layer to form on during initial ion insertion, preventing mechanicalchanges and breakage during subsequent cycles. It may be advantageous tohave a protective layer (such as carbon) on the active material that ismore compatible with traditional electrolytes (e.g., electrolytescomprising carbonate solvents, such as ethylene carbonate (EC) orfluoroethylene carbonate (FEC) in the case of Li-ion batteryapplications), that does not change dimensions significantly (e.g., bymore than about 10%) during charge-discharge cycling, in contrast to,for example, silicon (which changes dimensions dramatically, by over200% in the case of metal ion insertion to the theoretically maximumlevel), and that is known to form a more stable SEI from the beginning.

Other types of shells and layers of shell materials may be employed forvarious purposes in different applications.

FIG. 3 illustrates another example battery electrode composition designincorporating a functional shell according to other example embodiments.As shown, the composite particle 300 of FIG. 3 includes the activematerial 102 and the porous, electrically-conductive scaffolding matrix104 within which the active material 102 is disposed, as well as a shell308 at least partially encasing the active material 102 and thescaffolding matrix 104. Here, the shell 308 includes an active materiallayer, rather than a protective layer as in the design of FIG. 2. It maybe advantageous for the active material 102 disposed within thescaffolding matrix to be formed from a first active material while theactive material shell layer 308 is formed from a second active material.

In general, two types of active materials may be utilized in suchcomposites: (i) a so-called “high-capacity” active material, whichundergoes significant volume changes during battery (or otherelectrochemical energy storage device) operation (e.g., greater thanabout 10%) and (ii) a “regular” or “moderate-to-low capacity” activematerial, which undergoes small volume changes during battery (or otherelectrochemical energy storage device) operation (e.g., smaller thanabout 8%). One common example of a “regular” active material is an“intercalation-type” material, where the electrolyte ions areinserted/extracted to/from the small openings (e.g., interstitialpositions) existing in such a material. In the case of a Li-ion battery,lithium metal oxides (such as lithium cobalt oxides, lithium manganeseoxides, lithium manganese cobalt oxides, lithium manganese nickel cobaltoxides, lithium metal phosphates, to name a few) are among examples ofsuch “intercalation-type” cathode materials and graphite or lithiumtitanate are among examples of such “intercalation-type” anodematerials. In the case of a Li-ion battery, conversion-type electrodes(such as metal fluorides, sulfides, oxides, nitrides, phosphides, andhydrides) or alloying-type electrodes (e.g., silicon, germanium, tin,lead, antimony, magnesium, and others) are among examples of such“high-capacity” active materials.

Accordingly, returning to FIG. 3, it may be advantageous to use twodifferent active materials for the active material 102 and the activematerial shell layer 308. In particular, the first active material forthe active material 102 may be selected as a high capacity activematerial having a substantially higher capacity relative to the secondactive material of the active material shell layer 308, which may beselected as a moderate-to-low capacity active material. In this way, ahybrid structure is provided that advantageously combines the highcapacity materials discussed above with low-to-moderate capacity activematerial(s) (e.g., less than about 400 mAh/g for Li-ion battery anodesand about 250 mAh/g for Li-ion battery cathodes).

The low-to-moderate capacity (e.g., intercalation-type) layer mayprovide high rate capability to the composite, while the higher capacityactive nanoparticles enhance the (ion storage) energy storage propertiesof the composite. As a result, battery electrodes produced fromcomposites of this type comprising a low capacity shell layer and highcapacity active nanoparticles distributed within a porous scaffoldingmatrix may offer higher energy density than conventional intercalationtype electrodes and higher power density than electrodes composed ofhigh capacity nanoparticles alone. In addition, such composites mayoffer enhanced structural stability because the low capacity shell layercommonly exhibits small volume changes (below about 8 vol. %) duringbattery operation.

FIG. 4 illustrates another example battery electrode composition designincorporating a functional shell according to other example embodiments.As shown, the composite particle 400 of FIG. 4 includes the activematerial 102 and the porous, electrically-conductive scaffolding matrix104 within which the active material 102 is disposed, as well as a shell408 at least partially encasing the active material 102 and thescaffolding matrix 104. Here, the shell 408 includes a porous layer(e.g., an electrically and ionically conductive porous carbon), ratherthan a protective layer as in the design of FIG. 2 or an active materiallayer as in the design of FIG. 3. In some designs, it may beadvantageous to provide the porous shell layer 408 with a differentporosity as compared to the scaffolding matrix 104, and in particular, asmaller average pore size than the scaffolding matrix 104.

In this way, advantages may be provided by having two types of porousstructures within a composite particle—one type in the core of thecomposite particle and another type in the shell layer of the compositeparticle. The core part can, for example, have larger pores and/or alarger fraction of the pores to maximize the volume fraction of thecomposite particle filled with high capacity active nanoparticles. Theouter shell layer can, for example, have smaller or fewer pores and amore rigid structure, which helps improve mechanical stability of theoverall composite particle. The outer shell layer may also have adifferent microstructure and surface chemistry, so that when infiltratedwith high capacity active nanoparticles, most of the nanoparticles willnucleate and grow in the core within the scaffolding matrix. In thiscase, the shell layer may have a smaller fraction of the highvolume-changing high capacity active particles, which again, in turn,improves the stability of the composite.

As discussed above with reference to FIG. 3, certain advantages may beprovided by using two different types of active materials in a compositeparticle in order to take advantages of their respective propertieswhile mitigating their respective drawbacks. Accordingly, when a porousshell layer is employed as in the design of FIG. 4, a second activematerial may be integrated into the resultant composite structure viathe pores of the shell. This arrangement is discussed in more detailbelow.

FIG. 5 illustrates another example battery electrode composition designincorporating a functional shell with a second active material accordingto other example embodiments. As shown, the composite particle 500 ofFIG. 5 includes the active material 102 and the porous,electrically-conductive scaffolding matrix 104 within which the activematerial 102 is disposed, as well as a shell 508 at least partiallyencasing the active material 102 and the scaffolding matrix 104. Here,the shell 508 includes a porous layer, as in the design of FIG. 4, butthe pores of the porous layer are at least partially filled with asecond active material different from the active material 102 disposedwithin the scaffolding matrix 104. Thus, in this example, the activematerial 102 disposed within the scaffolding matrix 104 may be formedfrom a first active material while at least some pores in the porouslayer of the shell 508 are infiltrated with a second active material.

As an example, the porous layer of the shell 508 may be infiltrated witha low-to-medium capacity (e.g., intercalation-type) active material thatexperiences small volume changes during cycling. In some applications(e.g., if used as an anode in Li-ion batteries that form an SEI duringbattery operation), this arrangement may further provide a stableplatform on which to form an electrolyte solvent impermeable layer toprevent solvent permeation into the scaffolding matrix. In cases wherethe porous layer material of the shell has a higher conductivity thanthe low-to-medium capacity active material, the active-materialinfiltrated shell in the design of FIG. 5 may provide improvedconductivity compared to a pure active material layer shell as in thedesign of FIG. 3.

In still other embodiments, the shell may be a composite materialcomprising multiple layers, such as two or more of the functional layersdescribed above, or other layers as desired for a given application.

FIG. 6 illustrates an example battery electrode composition designincorporating a multi-layered functional shell according to otherexample embodiments. As shown, the composite particle 600 of FIG. 6includes the active material 102 and the porous, electrically-conductivescaffolding matrix 104 within which the active material 102 is disposed,as well as a multi-layered composite material shell having an innerlayer 610 and an outer layer 612, each at least partially encasing theactive material 102 and the scaffolding matrix 104. The two layers 610,612 are shown for illustration purposes only, as additional interveninglayers may be utilized as desired, and each layer may be selected toprovide different functionality for different applications.

In the particular example illustrated in FIG. 6, the inner layer 610 isa porous layer having a smaller average pore size than the scaffoldingmatrix 104. Formation of an inner porous layer shell in this way, withpores sufficiently smaller than that of the underlying scaffoldingmatrix, may help simplify the deposition of additional outer layers. Theouter layer 612 in this example is a protective layer formed from amaterial that is substantially impermeable to electrolyte solventmolecules, as in the design of FIG. 2.

FIG. 7 illustrates another example battery electrode composition designincorporating a multi-layered functional shell according to otherexample embodiments. As shown, the composite particle 700 of FIG. 7includes the active material 102 and the porous, electrically-conductivescaffolding matrix 104 within which the active material 102 is disposed,as well as a multi-layered composite material shell having an innerlayer 710 and an outer layer 712, each at least partially encasing theactive material 102 and the scaffolding matrix 104. In the particularexample illustrated in FIG. 7, the inner layer 710 is again a porouslayer having a smaller average pore size than the scaffolding matrix104, as in the design of FIG. 6. The outer layer 712 in this example,however, is an active material layer formed from an active material thatis different from the active material disposed within the scaffoldingmatrix 104, as in the design of FIG. 3.

FIG. 8 illustrates an alternative example battery electrode compositiondesign according to other example embodiments. As shown, the compositeparticle 800 of FIG. 8 includes the active material 102 and the porous,electrically-conductive scaffolding matrix 104 within which the activematerial 102 is disposed, as in the design of FIG. 1, but is formedaround an active material core 806. Here, the active material 102disposed within the scaffolding matrix 104 may be formed from a firstactive material while the active material core 806 may be formed from asecond active material.

As discussed above in relation to the active material shell layer 308 ofFIG. 3, it may likewise be advantageous to use two different activematerials for the active material 102 and the active material core 806.In particular, the first active material for the active material 102 maybe selected as a high capacity active material having a substantiallyhigher capacity relative to the second active material of the activematerial core 806, which may be selected as a moderate-to-low capacityactive material. In this way, a hybrid structure is provided thatadvantageously combines the benefits of the high capacity materialsdiscussed above with those of a low-to-moderate capacity active materialparticle(s).

In particular, the low-to-moderate capacity (e.g., intercalation-type)particles may provide high rate capability to the resultant composite,while the high capacity active nanoparticles enhance the (ion storage)energy storage properties of the composite. As a result, batteryelectrodes produced from composites of this type comprising low capacityparticles and high capacity active nanoparticles distributed within aporous scaffolding matrix may offer higher energy density thanconventional intercalation type electrodes and higher power density thanelectrodes composed of high capacity nanoparticles alone. In addition,such composites may offer enhanced structural stability because lowcapacity particles commonly exhibit low volume changes (below about 8vol. %) during battery operation.

It will be appreciated that in addition to the singularly illustratedparticle making up the active material core 806 in FIG. 8, several suchparticles may be utilized in combination as desired. Moreover, suchparticles may be of different chemistry and blended/mixed together in avariety of forms to create composite particles providing the advantagesdescribed herein through an interpenetrating network of different typesof active materials. By using a combination of different particles, boththe voltage profile of an electrode and the power density vs. energydensity of an electrode can be tuned to desired specifications.

Several example methods of fabrication for hybrid composite structuresof the type described above are provided below. The methodologies may besimilar, at least in some respects, to the previously discussedfabrication methods.

According to one example method, high capacity active particles may beintroduced into a pre-fabricated porous carbon scaffold shell aroundintercalation-type low capacity active material particles via chemicalvapor deposition (CVD).

According to another example method, high capacity active particles maybe introduced into a pre-fabricated porous carbon scaffold shell aroundintercalation-type low capacity active material particles via vaporinfiltration and/or capillary condensation.

According to another example method, active particles may be introducedinto a pre-fabricated porous carbon scaffold shell by: (i) dissolvingactive particles or active particle precursors in a solvent; (ii)infiltration of the solution into the pores of pre-fabricated porouscarbon matrix under normal pressure or at increased pressures or undervacuum; (iii) evaporation of the solvent; and (iv) (if needed)transformation of the precursor into the active particles. In somecases, some of these steps may be repeated to increase the total amountof the introduced nanoparticles of active material into the porouscarbon matrix.

According to another example method, active particles are introducedinto a pre-fabricated porous carbon scaffold shell by: (i) dissolvingactive particles or active particle precursors in a solvent; (ii)infiltration of the solution into the pores of pre-fabricated porouscarbon matrix under normal pressure or at increased pressures or undervacuum; (iii) heterogeneous precipitation of nano particles on the innercarbon surface from the solution by, for example, adding a non-solvent,changing ionic strength or pH of the solution, or changingtemperature/pressure of the system; and (iv) (if needed) transformationof the precursor into the active particles. In some cases, some of thesesteps may be repeated to increase the total amount of the introducednanoparticles of active material into the porous carbon matrix.

According to another example method, active particles may be introducedinto a pre-fabricated porous carbon scaffold shell by infiltration ofnanoparticles of active material into the pores of pre-formed porouscarbon using a suspension infiltration method under normal pressure, atincreased pressures, or under vacuum.

According to another example method, the following may be performed: (i)active nanoparticles may be first adsorbed onto the surface of thenanoparticles of a polymeric precursor for carbon formation (e.g., byintroduction of the opposite charge on the surface of the activenanoparticles and the surface of the polymer precursor nanoparticles);(ii) the active nanoparticle-polymer mixture may be coated on thesurface of large size (e.g., greater than about 0.5 micron in diameter)intercalation-type low capacity active material particles; (iii) thermaltreatment that induces carbonization of the polymer precursor and theformation of the nanocomposite shell comprising active nanoparticles,carbon and nanopores; and (iv) optional activation to increase thevolume of pores. In another example, after the nanoparticle deposition,the composite polymer nanoparticles may be covered with anothercarbon-forming polymer layer by the electrostatic adsorption of apolymer having opposite surface charge than that of the particles.

According to another example method, the following may be performed: (i)active nanoparticles and polymer precursor nanoparticles may becoagulated heterogeneously from a solution/suspension onto the surfaceof the large size (e.g., greater than about 0.5 micron in diameter)intercalation-type low capacity active material particles; (ii) thermalannealing (carbonization) to form the nanocomposite shells withnanoparticles uniformly distributed within carbon and pores; and (iii)optional activation to increase the volume of pores. In another example,the large size nanoparticles covered with active/polymer nanoparticlesmay be covered with another layer of a carbon-forming polymer beforecarbonization.

According to another example method, the following may be performed: (i)active nanoparticles may first be dispersed in a monomer or polymersolution; (ii) the produced suspension mixed with large size (e.g.,greater than about 0.5 micron in diameter) intercalation-type lowcapacity active material particles may be emulsified (e.g., in water) toproduce spherical high capacity nanoparticle low-capacityparticle-polymer colloids in water; (iii) the monomer in the colloidsmay be polymerized (or solvent may be extracted from a polymer solution)to produce the spherical composite particles composed of active highcapacity nanoparticles, low capacity particles, and a polymer; (iv) uponwater evaporation the composite particles may be carbonized; and (v) theproduced carbon-active nanoparticle composite may (optionally) beactivated to increase the volume of pores. In another example,polymerization may be conducted in a non-aqueous solvent for the monomerwhich is a non-solvent for the polymer being synthesized. During thepolymerization, the polymer particles may be formed by a precipitationmechanism. In course of the precipitation, polymerization if the activenanoparticles/large particles may become captured inside the polymerparticles. Upon solvent evaporation, the composite particles may becarbonized.

According to another example method, the following may be performed: (i)water with active high capacity particle precursors and low capacityactive particles may be emulsified in a monomer solution; (ii) theproduced mixture may be emulsified in water again to produce colloids ofthe monomer solution (inside of which there may be colloids of activeparticle precursor); (iii) the monomer may be polymerized producingnear-spherical polymer particles containing the distribution ofprecursors of active particles and comprising active particles; (iv) theproduced emulsion may be dried, calcinated/carbonized to produce porouscarbon particles with incorporated particles of active material; and (v)the produced carbon-active nanoparticle composite may be (optionally)activated to increase the volume of pores. An analogous approach may berealized in a non-aqueous medium as mentioned above.

According to another example method, the following may be performed: (i)an active particle precursor may be dissolved in an organic solventalong with a suitable carbon forming polymer; (ii) the solution may bemixed with low capacity active particles to form a suspension; (iii) thesuspension may be mixed with an excess of a non-solvent for the activeparticle precursor and the polymer, and composite particles may beformed by precipitation; and (iv) the produced particles may be dried,and calcinated/carbonized to produce porous carbon particles withincorporated nanoparticles of active material. In another example, theprecipitation may be conducted via changing the ionic strength or pH ofthe solution, or changing the temperature/pressure of the system.

It will further be appreciated that the active material core design ofFIG. 8 may be used in combination with any of the shell designsdiscussed above. Two examples are discussed below with regard to FIGS.9-10.

FIG. 9 illustrates an example battery electrode composition designincorporating an active material core and a functional shell accordingto other example embodiments. As shown, the composite particle 900 ofFIG. 9 includes the active material 102 and the porous,electrically-conductive scaffolding matrix 104 within which the activematerial 102 is disposed, as well as the shell 208 at least partiallyencasing the active material 102 and the scaffolding matrix 104, as inthe design of FIG. 2. The composite particle 900 of FIG. 9 still furtherincludes the active material core 806, as in the design of FIG. 8. Inthis example, the shell 208 is specifically, or otherwise includes, aprotective layer formed from a material that is substantiallyimpermeable to electrolyte solvent molecules.

FIG. 10 illustrates another example battery electrode composition designincorporating an active material core and a functional shell accordingto other example embodiments. As shown, the composite particle 1000 ofFIG. 10 includes the active material 102 and the porous,electrically-conductive scaffolding matrix 104 within which the activematerial 102 is disposed, as well as the multi-layered compositematerial shell having an inner layer 710 and an outer layer 712, as inthe design of FIG. 7, each at least partially encasing the activematerial 102 and the scaffolding matrix 104. The composite particle 1000of FIG. 10 still further includes the active material core 806, as inthe design of FIG. 8. In this example, the inner shell layer 710 is aporous layer having a smaller average pore size than the scaffoldingmatrix 104, while the outer layer 712 is an active material layer formedfrom an active material that is different from the active materialdisposed within the scaffolding matrix 104, but which may be the same asthe active material of the active material core 806.

In some applications it may be desirable to further increase iontransport within the composite particle structure. It may therefore beadvantageous to provide so-called external “channel” pores designed toprovide faster ion diffusion and thus improve power performancecharacteristics.

FIG. 11 illustrates an example battery electrode composition designincorporating external channel pores according to other exampleembodiments. As shown, the composite particle 1100 of FIG. 11 includesthe active material 102 and the porous, electrically-conductivescaffolding matrix 104 within which the active material 102 is disposed,as in the design of FIG. 1, and further includes channel pores 1114extending from an outer surface of the scaffolding matrix 104 towardsthe center of the scaffolding matrix 104. In this way, the channel pores1114 provide channels for faster diffusion of the ions from theelectrolyte into the active material 102 disposed within the scaffoldingmatrix 104 by reducing the average diffusion distance of the ions.

More specifically, the pores in the scaffolding matrix may be relativelysmall (for example, on the order of about 0.5-5 nm) and, in some cases(when, for example, the electrolyte infiltrates the pores) provide slowion transport into the core of the composite particle. By forming largerchannel pores (for example, on the order of about 10-30 nm) propagatingfrom the external surface of the particle into the core and havingsignificantly faster ion diffusion rates, the rate performance of anelectrode composed of such particles may be significantly improved. Insome cases, for example when the electrolyte infiltrates the smallerscaffolding matrix pores and partially decomposes at low potentials toform an SEI layer having relatively low ionic conductivity, the channelpores partially free from the SEI similarly provide high rateperformance.

In some embodiments, the channel pores may be filled with one or morefunctional materials to provide other benefits as desired for a givenapplication.

FIG. 12 illustrates an example battery electrode composition designincorporating external channel pores and a filler material according toother example embodiments. As shown, the composite particle 1200 of FIG.12 includes the active material 102 and the porous,electrically-conductive scaffolding matrix 104 within which the activematerial 102 is disposed, as well as the channel pores 1114 extendingfrom an outer surface of the scaffolding matrix 104 towards the centerof the scaffolding matrix 104, as in the design of FIG. 11. Thecomposite particle 1200 of FIG. 12 still further includes a fillermaterial 1216 such that at least some of the external channel pores 1114are filled with the filler material 1216. In this example, the fillermaterial 1216 is specifically, or otherwise includes, an active materialthat is different from the active material 102 disposed within thescaffolding matrix 104. This second type of active material may besimilar to that described above with reference to FIG. 3, and mayprovide similar advantages by having two types of active materialswithin a composite particle, including improved structural stability ofthe particle, providing fast ion access to the scaffolding matrix,further reducing particle volume changes during battery operation,blocking electrolyte solvent access to the core of the particle, and soon.

FIG. 13 illustrates another example battery electrode composition designincorporating external channel pores and a filler material according toother example embodiments. As shown, the composite particle 1300 of FIG.13 includes the active material 102 and the porous,electrically-conductive scaffolding matrix 104 within which the activematerial 102 is disposed, as well as the channel pores 1114 extendingfrom an outer surface of the scaffolding matrix 104 towards the centerof the scaffolding matrix 104 and a filler material 1316 such that atleast some of the external channel pores 1114 are filled with the fillermaterial 1316, as in the design of FIG. 12. In this example, however,the filler material 1316 is specifically, or otherwise includes, aporous material having a different microstructure than the scaffoldingmatrix (e.g., different pore size, pore density, etc.). The porousmaterial may be similar to that described above with reference to FIG.4, and may provide similar advantages by having two types of porousstructures within a composite particle.

FIG. 14 illustrates another example battery electrode composition designincorporating external channel pores and a filler material according toother example embodiments. As shown, the composite particle 1400 of FIG.14 includes the active material 102 and the porous,electrically-conductive scaffolding matrix 104 within which the activematerial 102 is disposed, as well as the channel pores 1114 extendingfrom an outer surface of the scaffolding matrix 104 towards the centerof the scaffolding matrix 104 and a filler material 1416 such that atleast some of the external channel pores 1114 are filled with the fillermaterial 1416, as in the designs of FIGS. 12 and 13. In this example,the filler material 1416 includes a porous material, as in the design ofFIG. 13, but the pores of the porous material are at least partiallyfilled with a second active material different from the active material102 disposed within the scaffolding matrix 104. This composite fillerarrangement may be similar to that described above with reference toFIG. 5, and may provide similar advantages by having the active material102 disposed within the scaffolding matrix 104 formed from a firstactive material while at least some pores in the porous filler material1416 are infiltrated with a second active material.

It will be appreciated that other types of filler materials may be usedas well for different applications. For example, when the electrolytedoes not infiltrate the smaller scaffolding matrix pores and when ionicconductivity of the scaffolding matrix is relatively low, the largerchannel pores may be filled either with another electrolyte (e.g., asolid electrolyte material) or, more generally, with an ionicallyconductive material to similarly provide higher rate performance to thecomposite particles.

It will further be appreciated that the channel pore designs of FIGS.11-14 may be used in combination with any of the shell designs discussedabove. Two examples are discussed below with regard to FIGS. 15-16.

FIG. 15 illustrates an example battery electrode composition designincorporating external channel pores and a functional shell according toother example embodiments. As shown, the composite particle 1500 of FIG.15 includes the active material 102 and the porous,electrically-conductive scaffolding matrix 104 within which the activematerial 102 is disposed, as well as the channel pores 1114 extendingfrom an outer surface of the scaffolding matrix 104 towards the centerof the scaffolding matrix 104, as in the design of FIG. 11. Thecomposite particle 1500 of FIG. 15 still further includes the shell 208at least partially encasing the active material 102 and the scaffoldingmatrix 104, as in the design of FIG. 2. In this example, the shell 208is specifically, or otherwise includes, a protective layer formed from amaterial that is substantially impermeable to electrolyte solventmolecules. In some designs it is advantageous for this shell to at leastpartially coat the inner walls of the channel pores.

FIG. 16 illustrates an example battery electrode composition designincorporating external channel pores, a filler material, and afunctional shell according to other example embodiments. As shown, thecomposite particle 1600 of FIG. 16 includes the active material 102 andthe porous, electrically-conductive scaffolding matrix 104 within whichthe active material 102 is disposed, as well as the channel pores 1114extending from an outer surface of the scaffolding matrix 104 towardsthe center of the scaffolding matrix 104 and the filler material 1316(e.g., a porous material) such that at least some of the externalchannel pores 1114 are filled with the filler material 1316, as in thedesigns of FIG. 13. The composite particle 1600 of FIG. 16 still furtherincludes the shell 208 at least partially encasing the active material102 and the scaffolding matrix 104, as in the design of FIG. 2, as wellas the filler material 1316. In this example, the shell 208 isspecifically, or otherwise includes, a protective layer formed from amaterial that is substantially impermeable to electrolyte solventmolecules.

It will be appreciated that the different composite particle structuresprovided herein can be formed in a variety of ways. Several exampleformation methods have already been provided herein, and several moreare described below.

FIG. 17 is a flowchart illustrating an example method of fabricating abattery electrode composition according to various example embodiments.In this example, an active material is provided to store and releaseions during battery operation (block 1710). As discussed above, thestoring and releasing of the ions may cause a substantial change involume of the active material. Accordingly, a porous,electrically-conductive scaffolding matrix is provided within which theactive material may be disposed (block 1720). As also discussed above,the scaffolding matrix structurally supports the active material,electrically interconnects the active material, and accommodates thechanges in volume of the active material.

The scaffolding matrix may be formed in a variety of ways. In oneexample illustrated here, the scaffolding matrix may be formed byforming a carbon-containing precursor (optional block 1722), oxidizing(e.g., to increase carbonization yield) and carbonizing thecarbon-containing precursor to form a carbonized particle (optionalblock 1724), and activating the carbonized particle at elevatedtemperature to form the scaffolding matrix (optional block 1726).Forming the scaffolding matrix may further comprise infiltration of theactive material into the scaffolding matrix (optional block 1728), whichmay be performed by (i) chemical vapor deposition, (ii) solutioninfiltration followed by solvent evaporation, (iii) solutioninfiltration followed by solvent evaporation and annealing, (iv)solution infiltration followed by precipitation during nonsolventaddition, (v) sol-gel, (vi) vapor infiltration, (vii) atomic layerdeposition, (viii) electroplating, (ix) melt infiltration, or othertechniques described herein.

According to various designs, a shell may also be formed at leastpartially encasing the active material and the scaffolding matrix(optional block 1730). The shell may be made substantially permeable tothe ions stored and released by the active material. The shell may alsobe formed as a composite material comprising an inner layer and an outerlayer. In one example, the inner layer may be a porous layer having asmaller average pore size than the scaffolding matrix. The outer layermay be a protective layer formed from a material that is substantiallyimpermeable to electrolyte solvent molecules, an active material layerformed from an active material that is different from the activematerial disposed within the scaffolding matrix, or other materiallayers discussed variously herein.

FIGS. 18-23 provide further examples of process steps that can beutilized for the fabrication of some of the described composite particlestructures.

FIG. 18 is a graphical flow diagram from a cross-sectional perspectivedepicting formation of an example composite particle of the typeillustrated in FIG. 1 or 3 according to certain example embodiments. Inthis example, carbon precursor particles (such as for example organicparticles, including polymer particles, carbohydrate particles, andothers) are first produced using one of several known methods, such asthose previously described (block 1810). By partial oxidation,carbonization, annealing in an inert environment, and activation, theseprecursor particles can be transformed into porous carbon particles(blocks 1820-1830). The pore size distribution and the porosity of thefinal particles can be controlled by multiple parameters, such as thepore size and pore volume present in the carbon precursor, by thecomposition and microstructure of the carbon precursor, by theoxidation, annealing, and activation conditions, and so on. Afterformation, the porous carbon scaffold can be infiltrated with highcapacity active particles using one of the gaseous or liquid chemistryroutes previously described or by using a combination of infiltrationapproaches (block 1840). Subsequently, an external shell may be formedof, for example, a low-to-moderate capacity (e.g., intercalation-type)active material by using one or a combination of previously describedmethods (chemical vapor deposition, sol gel, precipitation, etc.) (block1850).

FIG. 19 is a graphical flow diagram from a cross-sectional perspectivedepicting formation of an example composite particle of the typeillustrated in FIG. 8 according to certain example embodiments. In thisexample, a carbon precursor (for example, a polymer) coating is firstapplied onto the surface of low-to-moderate capacity active particles(block 1910). After polymer partial oxidation and at least partialcarbonization (at temperatures below the thermal stability limit of theactive particles) (block 1920), the porous scaffold is formed (block1930). In order to enhance the scaffold porosity, the material can befurther activated (similarly, under such conditions that do not inducesignificant damage into the active particle(s) core). Subsequently, theporous scaffold is infiltrated with high capacity active particles(block 1940).

FIG. 20 is a graphical flow diagram from a cross-sectional perspectivedepicting formation of an example composite particle of the typeillustrated in FIG. 4, 5, or 7 according to certain example embodiments.In this example, after the formation of scaffold particles infiltratedwith active material nanoparticles (blocks 2010-2040, corresponding toblocks 1810-1840 and described in more detail above), another (largelyexternal) layer of a carbon precursor (such as a polymer) is introduced(block 2050) and carbonized under conditions which do not induceundesirable damages or changes in chemical composition of the activenanoparticles (block 2060). As a result, the particles are provided witha porous shell layer. The outer surface of such a layer can be sealed byan electrolyte ion permeable and solvent impermeable layer (not shown).In some designs, an external shell of low-to-moderate capacity (e.g.,intercalation-type) active material is deposited on the top orinfiltrated within the top porous scaffold shell layer (block 2070).

FIG. 21 is a graphical flow diagram from a cross-sectional perspectivedepicting formation of an example composite particle of the typeillustrated in FIG. 5 or 7 according to certain example embodiments. Inthis example, the active particles are infiltrated into the porouscore-shell scaffold (block 2170) after the formation of a porous shelllayer (blocks 2110-2160). The advantage of this approach is thatconditions that would normally damage active particles (e.g., highprocessing temperatures or processing under hydrogen-containing oroxygen-containing environment) can be utilized for the formation of thescaffold particles. Additional shell layers may be added as desired(block 2180).

FIG. 22 is a graphical flow diagram from a cross-sectional perspectivedepicting formation of an example composite particle of the typeillustrated in FIG. 4 according to certain example embodiments. In thisexample, a shell layer of a porous scaffold is introduced (block2230-2240) after carbonization of the scaffold core (blocks 2210-2220),but before activation of the scaffold core. The activation step (block2250) is conducted on scaffold particles comprising both the carbonizedcore and carbonized shell. The final step involves infiltration ofactive particles into the pores of the scaffold (block 2260).

FIG. 23 is a graphical flow diagram from a cross-sectional perspectivedepicting formation of an example composite particle of the typeillustrated in FIG. 4 or 6 according to certain example embodiments. Itis similar to what is described by FIG. 22 (blocks 2310 and 2330-2350),but the core-shell carbon precursor particles are formed before theircarbonization and subsequent activation (block 2320). Further, aspreviously described, after infiltration by active particles, the outerlayer of the scaffold can be sealed with a layer that is essentiallypermeable to electrolyte ions but largely impermeable to electrolytesolvent (block 2360). Such a layer may also be made electricallyconductive (e.g., by comprising sp² bonded carbon).

FIG. 24 shows SEM and TEM images of an example carbon scaffold particlefabricated with silicon nanoparticles deposited therein.

FIG. 25 illustrates an example battery (e.g., Li-ion) in which thecomponents, materials, methods, and other techniques described herein,or combinations thereof, may be applied according to variousembodiments. A cylindrical battery is shown here for illustrationpurposes, but other types of arrangements, including prismatic or pouch(laminate-type) batteries, may also be used as desired. The examplebattery 2501 includes a negative anode 2502, a positive cathode 2503, aseparator 2504 interposed between the anode 2502 and the cathode 2503,an electrolyte (not shown) impregnating the separator 2504, a batterycase 2505, and a sealing member 2506 sealing the battery case 2505.

The forgoing description is provided to enable any person skilled in theart to make or use embodiments of the present invention. It will beappreciated, however, that the present invention is not limited to theparticular formulations, process steps, and materials disclosed herein,as various modifications to these embodiments will be readily apparentto those skilled in the art. That is, the generic principles definedherein may be applied to other embodiments without departing from thespirit or scope of the invention.

The invention claimed is:
 1. A battery anode electrode composition,comprising: a composite particle, comprising: Si-comprising activematerial that is electrochemically reactive with metal ions duringbattery operation; and a porous scaffolding matrix comprising amonolithic particle within which the Si-comprising active material is atleast partially disposed, wherein the porous scaffolding matrixelectrically interconnects the Si-comprising active material.
 2. Abattery anode electrode composition of claim 1, further comprising: acoating to inhibit contact of solvent molecules of an electrolyte withthe Si-comprising active material.
 3. A battery anode electrodecomposition of claim 1, further comprising: a coating permeable to themetal ions.
 4. A battery anode electrode composition of claim 1, whereinthe monolithic particle comprises carbon.
 5. A battery anode electrodecomposition of claim 1, wherein the metal ions comprise one or more of:Li⁺, Na⁺, Mg²⁺, or Ca²⁺.
 6. A cylindrical, prismatic, or pouch battery,comprising: an anode and a cathode, wherein the anode comprises thebattery anode electrode composition of claim
 1. 7. A battery anodeelectrode composition of claim 1, wherein the porous scaffolding matrixcomprises one or more micropores with a first pore size below 2 nm andone or more mesopores with a second pore size between 2 nm and 50 nm. 8.A battery anode electrode composition of claim 7, wherein the metal ionscomprise one or more of: Li⁺, Na⁺, Mg²⁺, or Ca²⁺.
 9. A cylindrical,prismatic, or pouch battery, comprising: an anode and a cathode, whereinthe anode comprises the battery anode electrode composition of claim 7.10. A battery anode electrode composition of claim 1, wherein a poresize of one or more pores in the porous scaffolding matrix is in a rangefrom 0.5 nm to 5 nm.
 11. A battery anode electrode composition of claim10, wherein the metal ions comprise one or more of: Li⁺, Na⁺, Mg²⁺, orCa²⁺.
 12. A cylindrical, prismatic, or pouch battery, comprising: ananode and a cathode, wherein the anode comprises the battery electrodecomposition of claim
 10. 13. A method of fabricating a battery anodeelectrode composition comprising at least one composite particle, themethod comprising: forming a porous scaffolding matrix by: carbonizing apolymer monolith to form a carbon monolith; forming at least onemonolithic particle from the carbon monolith; activating the at leastone monolithic particle; and introducing Si-comprising active materialinto the at least one monolithic particle.
 14. A method of fabricating abattery anode electrode composition comprising a composite particle, themethod comprising: forming a porous scaffolding matrix comprising amonolithic particle within which Si-comprising active material is atleast partially disposed, wherein the Si-comprising active material iselectrochemically reactive with metal ions during battery operation, andwherein the porous scaffolding matrix electrically interconnects theSi-comprising active material.
 15. The method of claim 14, wherein theporous scaffolding matrix comprises one or more micropores with a firstpore size below 2 nm and one or more mesopores with a second pore sizebetween 2 nm and 50 nm.
 16. The method of claim 14, wherein the metalions comprise one or more of: Li⁺, Na⁺, Mg²⁺, or Ca²⁺.
 17. A method offabricating a battery anode electrode composition comprising a compositeparticle, the method comprising: forming a porous scaffolding matrix by:carbonizing a precursor particle to form a carbonized particle; andactivating the carbonized particle; and introducing Si-comprising activematerial into the matrix, wherein the Si-comprising active material iselectrochemically reactive with metal ions during battery operation. 18.The method of claim 17, wherein the metal ions comprise one or more of:Li⁺, Na⁺, Mg²⁺, or Ca²⁺.
 19. The method of claim 17, additionallycomprising: processing the precursor particle, wherein the processing ofthe precursor particle is done before carbonizing the precursorparticle.
 20. The method of claim 19, wherein the processing of theprecursor particle comprises oxidizing the precursor particle.
 21. Themethod of claim 17, further comprising: covering the composite particlewith a polymer layer.
 22. The method of claim 21, wherein the polymerlayer is carbon forming.